1. Field of the Invention
The present invention generally relates to the field of laser treatment of tissue, and particularly, to a system and method for creating microablated channels in skin. The present invention is more particularly directed to treating subsurface tissue through the created channels. By treating subsurface tissue through uniquely created channels, skin may be treated with heretofore unrealized results.
2. Description of the Related Art
Skin is primarily made of an outer layer, or epidermis, that has a depth of approximately 100/an from the outer surface of the skin and an inner layer, or dermis, that has depth of approximately 3000 fm from the outer surface of the skin. As used herein, “dermal tissue” or “skin” refers to both the dermis and epidermis layers.
There is ongoing demand for procedures to improve skin defects. Such improvements include reducing wrinkles, reducing dyschromia (a variety of abnormalities or irregularities of skin color resulting from, inter alia, irregular pigment distribution, dilated blood vessels, etc.) and etc. A wide variety of skin treating techniques have been introduced in recent years for attempting to achieve this objective. The skin treating techniques that have been employed may be generally categorized into two general types of treatment: ablative laser skin resurfacing (“LSR”) and non-ablative collagen remodeling (“NCR”). LSR generally may result in fairly extensive thermal damage to either the epidermis and/or the dermis. NCR, on the other hand, is designed to avoid thermal damage of the epidermis.
Nevertheless, LSR is an effective laser treatment for treating skin. A typical LSR procedure comprises thermally damaging a region of the epidermis and a corresponding lower region of the dermis for promoting wound healing. Electromagnetic energy is directed towards a region of skin, thereby ablating the skin and removing both epidermal tissue and dermal tissue. Combining LSR with a pulsed laser, for example a CO.sub.2 or an Er:YAG laser, is typically referred to as laser resurfacing or ablative resurfacing. This is considered to be an effective treatment protocol photo aged or chronically aged skin, scars, superficial pigmented lesions, stretch marks, and/or superficial skin lesions. Major drawbacks include, however, edema, oozing, and burning discomfort up to the first fourteen (14) days after treatment. Such drawbacks are unacceptable for many patients. A further problem with LSR procedures is that they are relatively painful. Therefore, they generally require an application of a significant amount of analgesia. While LSR of relatively small areas can be performed under local anesthesia, LSR procedures that include relatively large areas frequently require general anesthesia or nerve blockage by multiple anesthetic injections.
Another limitation of LSR is that ablative laser resurfacing generally cannot be performed on the patients having dark complexions. Ablation of pigmented epidermis tissue can cause severe cosmetic disfigurement to patients having a dark complexion. Such disfigurement can last from several weeks up to years. This is generally considered to be unacceptable by most patients and physicians. Yet another limitation of LSR is that ablative resurfacing generally has a greater risk of scarring in areas other than the face and result in an increased incidence of an unacceptable scar formation because the recovery from skin injury within these areas is not very effective.
Several NCR techniques have attempted to overcome the aforesaid problems associated with LSR procedures. These techniques may be variously referred to as non-ablative resurfacing, non-ablative subsurfacing, or non-ablative skin remodeling. Such NCR techniques generally use non-ablative lasers, flash lamps, or radio frequency current for damaging the dermal tissue and avoiding damage to the epidermal tissue. NCR techniques apply the concept that it is the thermal damage of the dermal tissues that is thought to induce wound healing. This results in biological repair and the formation of new dermal collagen which in turn can result in decreased photoaging related structural damage. Avoiding the epidermal damage by using NCR techniques may also decrease both the severity and the duration of treatment related side effects, for example, post procedural oozing, crusting, pigment changes, and the incidence of infections.
Treating skin using the NCR method involves heating selective portions of dermal tissue within the dermal layer for inducing wound healing without damaging the epidermis above. By cooling the surface of the skin and focusing electromagnetic energy, for example a laser beam, a selected dermal damaged region can be achieved while leaving the epidermis undamaged. Using non-ablative lasers for damaging the dermis while leaving the epidermis undamaged is common to NCR treatment methods. Generally, using non-ablative lasers result in deeper dermal penetration depths as compared to the ablative lasers than the superficially-absorbed ablative Er:YAG and CO2 lasers used in typical LSR procedures. Further, when NCR techniques are used, they generally do not have the undesirable side effects characteristic of the LSR treatment, such as the risk of scarring or infection. Examples of NCR techniques and apparatus are disclosed by Anderson et al. in U.S. Patent Publication No. 2002/0161357.
Although these NCR techniques may avoid epidermal damage, a major drawback of this method is its limited effectiveness. For example, this is significantly less improvement of photoaged skin or scars after the NCR treatment than when LSR ablative techniques is used. In fact, even when multiple NCR treatments are employed, improvement in the patient's skin is often far below expectations. In addition, improvement is often delayed for several months when a series of treatment procedures are used. Although NCR techniques have been found to be moderately effective for wrinkle removal, they have generally not been found to be effective for dyschromia.
Another problem with using a NCR technique is the limited breadth of acceptable treatment parameters for safe and effective treatment of dermatological disorders. This is because NCR procedures generally rely on an optimum coordination of laser energy and cooling parameters. This results in an unfavorable temperature profile in the skin. An unfavorable temperature profile consequently results in either no therapeutic effect on one hand, or scar formation due to the overheating of a relatively large volume of the tissue, on the other.
A problem that is common to both ablative and non-ablative resurfacing procedures is that they do not significantly use keratinocytes, which play an active role in the wound healing response. Keratinocytes release cytokines when the keratinocyte is damaged. Cytokines encourage wound healing. For example, during ablative resurfacing procedures, keratinocytes are removed from the skin along with the epidermis. This removes keratinocytes entirely from the healing process altogether. During non-ablative procedures, keratinocytes, located in the epidermis, are not damaged at all and thus do not release cytokines for aiding the healing process.
Accordingly, there is now provided with this invention an improved system and method for treating skin that effectively overcomes the aforementioned difficulties and longstanding problems inherent in using either a LSR or a NCR procedure. These problems have been solved in a simple, convenient, and highly effective way by which to treat skin.